The natural history of plants, their forms, growth, reproduction, and distribution; . e ridges (see figs. 87 and 88). The greater part of each ridge consists of green tissue. The stomata on theridge only open on the sloping sides facing the grooves. Neither the crests of theridges nor the lower surface of the leaf exhibit a single stomate. The apex is withoutchlorophyll, and almost always has a border of elongated cells with strong elastic FORM AND POSITION OF THE TRANSPIRING LEAVES AND BRANCHES. 341 walls under the epidermis; the same thing occurs on the under side of the leaf (^. the bas
The natural history of plants, their forms, growth, reproduction, and distribution; . e ridges (see figs. 87 and 88). The greater part of each ridge consists of green tissue. The stomata on theridge only open on the sloping sides facing the grooves. Neither the crests of theridges nor the lower surface of the leaf exhibit a single stomate. The apex is withoutchlorophyll, and almost always has a border of elongated cells with strong elastic FORM AND POSITION OF THE TRANSPIRING LEAVES AND BRANCHES. 341 walls under the epidermis; the same thing occurs on the under side of the leaf (^. the base of the ridges), which is formed of one or several layers of cells withoutchlorophyll, but furnished with thickened walls. The closing of the leaf is not sosimple here as in the Seslerias. There the leaf-folding only produced a single deepchannel, widened at its base; in the fescue-grasses all the small grooves betweenthe ridges become narrowed by the closing, by the upward inclination of theright and left halves of the leaf, those adjoining the central ridge to the greatest. Fig. 86.—Folding of Grass-leaves. 1 Vertical section through an open leaf of the thin-leaved Moor-grass (Sesleria tenuifolia). « Vertical section througha closed leaf; x40. » Portion from the centre of an open leaf; x300. extent, those in the neighbourhood of the approximated margins in a lesser degree(see fig. 88^). Since the stomata lie on the sides of the ridges, it is obvious thattranspiration is checked to the utmost by the closing and consequent approximationof the opposite sides of each groove. In individual cases among various fescue-grasses are to be found manifolddifferences in the number and shape of the ridges, also with respect to the formationof the under surface of the leaf, and most of all in the form assumed by the leaf inits expanded condition. There is a large group of festucas which are said to bepoisonous by the shepherds in the mountain regions of Spain, and in the Alps, the
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbotany, bookyear1902
